She told The Sun newspaper: "I was on my own reading a magazine. I felt people behind me taking pictures. I could hear them all talking about me and laughing about me and I got upset.
"It's nothing to do with the lounge, I swear on the Bible. I got upset with the man saying, 'You are not fit to travel, you are crying'. I really lost my temper."
Miss Palmer-Tomkinson told the newspaper she then tried to run back through security, which is why she claims she was arrested and handcuffed.
The weary-looking socialite was also pictured on Sunday leaving her 4 million pound (NZ$8 million) flat in Kensington, west London, before checking into another flight to Zurich at Britain's busiest airport.
Miss Palmer-Tomkinson, who has a history of drink and drug problems, had been due to fly out to the exclusive ski resort of Klosters in Switzerland to celebrate her birthday before the incident.
The socialite - the goddaughter of Prince Charles - is thought to have been cautioned and released without charge, before returning to the airport a day later.
She was arrested under Section 5 of the Public Order Act 1986, which involves people using "threatening, abusive or insulting words or behaviour, or disorderly behaviour" in front of others.
'She completely lost control'
One witness told The Sun: "She had completely lost all control and she was screaming at officers.
"They had no choice but to arrest for her own and everyone else's safety."
The dramatic arrest was captured on video with onlookers describing her as "ballistic".
In the footage, Miss Palmer-Tomkinson can be seen arguing with a male and female police officer.
She then becomes so frustrated that she rips out a chunk of her own hair extensions and flings them at the officers' feet amid a storm of four-letter abuse.
As a third officer moves in, Miss Palmer-Tomkinson - who turns 43 tomorrow - tries to flee, screams "f*** off" and hurls her coat on the floor as they stop her.
Five more officers then arrive and, sobbing and screaming, the former model is restrained and handcuffed.
In her rage, she also allegedly ripped a security badge from a British Airlines manager.
But the socialite claimed in a tweet yesterday: "This news is inaccurate - I was not refused entrance to the first-class lounge. It was not the reason nor was It ever addressed."
'She went ballistic'
The Sun reported that police were called when she attempted to go back through security the wrong way.
Another onlooker added:"She went ballistic, she screamed 'I can't f****** believe you are treating me like this'."
Last night, Miss Palmer-Tomkinson claimed she had not been drinking at the time and that a panic attack had triggered her behaviour.
She said: "I was not drunk, there was no disorderly; I was cautioned and I saw a doctor, they were nice to me."
She flew out to Switzerland on Sunday night.
Earlier this year, Miss Palmer-Tomkinson gave an interview in which she claimed to be a recluse.
She said nowadays she hardly ever leaves her home because of anxiety and that the problem has become so severe that she has only gone outside three times this year.
Socialite's paranoia and anxiety
In an interview with talk show host Jeremy Kyle, she said she checked herself back to rehab two years ago after a nervous breakdown triggered by paranoia and anxiety.
She also claimed that the experience has left her terrified to touch drugs again, and that she has seen a therapist every week for the last nine years.
Her battle with drugs has been well-documented. In 1999, Miss Palmer-Tomkinson spent time in a rehabilitation centre, the Meadows, in Arizona, after she made a disorientated appearance on the Frank Skinner show.
She was forced her to undergo reconstructive surgery on her nose after it collapsed in 2006 - damage which needed a further procedure in 2011.
The former party girl, who admits she once had a 400 pound-a-day (NZ$806) cocaine habit, has also become infamous for her string of failed relationships.
After being linked to the likes of Robbie Williams and James Blunt, she now claims not to want a boyfriend - because she cannot stand the way men eat.
A Scotland Yard spokesman said: "Police at Heathrow Terminal 5 were made aware of disturbance in the forecourt of the building at approximately 3.30pm on Saturday, December 20.
"Officers arrived at the scene and arrested a 42-year-old woman. She was taken to a west London police station and subsequently accepted a caution under section 5 of the Public Order Act 1986."
- Daily Mail
